ScienceShot

ScienceShot: Alien World Is More Earth-Like Than Any Found

Astronomers have discovered an alien world that’s more Earth-like in its size and composition than any ever found. It’s so close to its star, however, and consequently so infernally hot, that it’s more of a hellish cousin to Earth than a twin. The object (shown above, in an artist's impression), christened Kepler-78b, is one of hundreds of worlds beyond our solar system detected by NASA’s Kepler spacecraft, which has been monitoring the brightness of some 150,000 stars in the Milky Way in search of planets orbiting them. The majority of these so-called exoplanets are gas giants—big balls of gas and dust that are several times larger in radius than Earth. But Kepler-78b is only 80% more massive than Earth and 20% larger in radius, two groups of researchers report online today in Nature. That makes it about as dense as Earth and suggests that it is composed of rock and iron. But the object’s distance from its star (which is somewhat smaller than our sun) is only about twice the star’s radius, which means that the star would loom on the horizon like a gigantic disk, filling up a large part of the sky. Not a bad view, if you didn’t mind being burned to a crisp.